Wells are generally drilled into a land surface or ocean bed to recover natural deposits of oil, gas, and other natural resources that are trapped in geological formations in the Earth's crust. Testing and evaluation of completed and partially finished wellbores have become commonplace, such as to increase well production and return on investment. Information about the subsurface formations, such as measurements of the formation pressure, formation permeability, and recovery of formation fluid samples, may be utilized for predicting the economic value, the production capacity, and the production lifetime of a subsurface formation.
Various downhole tools and/or sensors may be utilized to perform such formation evaluations. For example, a resistivity tool may be utilized to measure the electrical resistivity of a formation surrounding the wellbore, because porous formations having high resistivity generally indicate the presence of hydrocarbons, while porous formations having low resistivity are generally water saturated. Resistivity tools utilize electrodes that are urged against a sidewall of the wellbore, or that are disposed at a distance (“standoff”) from the sidewall, and that emit and receive electrical energy through the formation to measure electrical current and/or potential to determine the formation resistivity.
Formation evaluation and other downhole tools and operations have become increasingly complex and expensive as wellbores are drilled deeper and through more difficult materials. Such wellbores present increasingly harsher environments, where temperature may exceed 250 degrees Celsius and pressure may exceed 30,000 pounds per square inch (PSI). Such extremes can damage the electrical connectors, sensors, and other electronic components of the downhole tools, and can cause downhole fluids to leak into the electronic components, and/or otherwise compromise the accuracy and even operation of the downhole tools.